Four studies involving assessment and intervention with preterm infants are proposed: The aim of Study I is to establish the reliability and validity of a new longitudinal neurobehavioral assessment procedure for preterm infants of 24 weeks conceptional age and up. Additionally, this study will document systematically the ontogeny of the expanding behavioral repertoire of preterm infants as they grow to term. Study II will assess whether waterbed flotation facilitates the organization of preterm infants' sleep and motility which are typically quite disorganized in these infants. Comparisons will be made between the infants' sleep and motility patterns on the standard incubator mattress, a nonoscillating waterbed, a continuously oscillating waterbed and a waterbed that oscillates intermittently either in the pattern of a maternal biological rhythm or at arbitrary intervals. Visual observations of sleep-wake states and the quality of the infants' movements will be made together with Vitalog recordings of the frequency and distribution of infant activity. Study III will determine whether waterbeds can increase both the duration and soundness of sleep and attenuate the restlessness and erratic motility frequently seen in infants on stimulant drugs for the treatment of apnea. The same protocol of observations and recordings will be used as in Study II. Study IV is a longitudinal intervention study which is to test whether compensatory movement stimulation through waterbed flotation enhances the development of preterm infants. Assessment of the sleep and motility, of neurobehavioral and other developmental functioning of randomly assigned experimental and control subjects will be made longitudinally up to 6 months post-term. The relevance of the studies' findings to the improvement of clinical services to preterm infants and the direct linkages to and collaboration with the infants' health care providers and the channels of dissemination of the research findings are outlined.